Method and apparatus for opening signatures

ABSTRACT

Signatures are opened up during travel on a conveyor in a substantially horizontal plane by means of suction heads which lift all sheets above the lower center sheets of successive signatures. The thus opened signatures are transferred onto a wedge-like support which extends into the space between the center sheets.

United States Patent [151 3,66 1,379 Dolfilli 1451 May 9, 1972 54] METHOD AND APPARATUS FOR 1,294,842 2/1919 Spiess ..270/55 x OPENING SIGNATURES 2,817,513 12/1957 Bellet a1 [72] Inventor: Leonardo Doliini, via Boscovich, Milan, ee H 0/56 Ux Italy FOREIGN PATENTS OR APPLICATIONS 1 Filed= y 14,1970 403,811 6/1966 Switzerland ..270/57 [21] App]. No.: 37,087

Primary Evaminer-Robert W. Mitchell Assistant Emminer-L. R. Oremland [30] Foreign Application Priority Data mmmey Michae| Striker May 26, 1969 Italy ..17341 A/69 [57] ABSTRACT [52] [1.8. CI ..270/54, 270/57 Signatures are opened up during travel on a conveyor in a [51 1 f h stantially horizontal plane by means ofsuction heads which lift [58] Fleldo Seal-c l 5 all sheets above the lower center sheets of successive signatures. The thus opened signatures are transferred onto a [56] References cued wedge-like support which extends into the space between the UNITED STATES PATENTS center Sheets- 3,008.705 1 1/1961 Heigl et al ..270/54 14 Claims, 19 Drawing Figures PATENTEDMM 9mm 3.661.379

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BY U I wi PATENTEBIWQIQR 3,661,379

SHEET 2 OF 5' INVENTOR. 0500404 006F101" PATENTEDMM 9 m2 SHEET 3 OF 5 INVENTOR.

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PATENTEDMAY 9|972 3,661,379 SHEET 0F 5 JNVENTOR. 4500429 W BACKGROUND OF THE INVENTION The present invention relates to a method and apparatus for manipulating signatures or sections which are about to be tied together to form books, pamphlets, magazines or analogous publications. More particularly, the invention relates to improvements in a method and apparatus for opening or spreading of signatures during transport or preparatory to transport of signatures to a bookbinding or like machine. The method and apparatus of the present invention can be utilized for high-speed opening of signatures during transport to automatic bookbinding machines, such as book sewing and wire stitcher machines.

In accordance with presently prevailing practice, signatures are fed downwardly so that the common edge of all sheets therein is the upper or trailing edge. The thus oriented signatures travel between two suction heads which engage the leading (lower) edges of outermost sheets whereby the signatures are opened up and are thereupon deposited on a triangular support so that the latter extends into the space between the two inner sheets of signatures and prevents the inner sheets from moving toward each other. The thus deposited signatures are thereupon fed to a book sewing or other machine.

A drawback of such apparatus is that signatures will not open between the two inner or central sheets if one or more additional sheets are pasted or otherwise attached thereto prior to movement between the suction heads. For example, if anadditional sheet is pasted to one outermost sheet of a simple four-sheet signature, the corresponding suction head will lift or spread theadditional sheet but not the adjoining sheets of the signature proper. The same applies if an additional sheet is pasted to one of the two inner sheets of a signature. .At the present time, such complex signatures are opened up by causing the additional sheet or sheets to extend beyond the sheets of the signature proper so that they may be engaged by further suction heads prior to transfer of such signatures onto the support. The projecting border portions (called bevel .elements) of additional sheets must be accessible to the corresponding suction heads; this presents problems during cutting of such sheets to size and contributes to the manufacturing cost. It is also known to reduce the size of sheets which are outwardly adjacent to such additional sheets so that the latter may be readily reached andgrasped by suction heads. This also contributes to initial cost because the sheets of the signatures must be specially prepared (cut to size) prior to or after attachment of additional sheets.

SUMMARY OF THE INVENTION An object of the invention is to provide a novel and improved method of opening signatures which can be resorted to for opening of simple as well as complex signatures with the same facility and within short periods of time.

Another object of the invention is to provide a method according to which a complex signature, with one or more additional sheets connected to the inside or to the outside of 'the basic section, can be opened up without any special preparation of the signature for such opening.

A further object of the invention is to provide an apparatus for openingof simple or complex signatures while the signatures travel toward a bookbinding or like machine.

An additional object of the invention.is to provide an apparatus which can be used for opening of simple, medium complex or very complex signatures.

Still another object of the invention is to provide an apparatus whose operation is fully automatic, which can open large numbers of signatures per unit of time, and which comprises a relatively small number of simple and readily accessible parts.

The method of thepresent invention is utilized for opening or spreading of signatures during transport to booltbinding or like machines and comprises the steps of conveying flattened signatures serially along an elongated path so that the common edges or ribs of their sheets extend transversely of the direction of travel and preferably-constitute the trailing edges of the respective signatures and that one of the two center or inner sheets of each signature overlies the other center sheet,

raising and tilting each sheet above the other center sheet while the signatures advance along the path so that the signatures are opened up between their center sheets, removing the .thus opened signatures from the path, and simultaneously holding the center sheets against pivotal movement toward each other.

The sheets above the other center sheet are preferably raised and pivoted by suction heads whereby such suction heads can raise a single pair of sheets, two or more pairs of sheets, and/orone or more additional sheets which are attached to the sheets in the upper part of a signature. For example, if an additional sheet is attached to and adjacent to the outer side of the uppermost sheet of a signature which is advanced past a series of suction heads, one of the suction heads lifts the additional sheet and another suction head lifts the pair of sheets below such additional sheet. In this way, the sheets or groups of connected sheets in the upper half of a travelling signature are pivoted away from the lower center sheet before the signature reaches the removing station.

The novel features which are considered as characteristic of the invention are set forth in, particular in the appended claims. The improved apparatus itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a fragmentary partly elevational and partly vertical sectional view of an apparatus which can be used for opening of simple or complex signatures;

'FIG. la is a schematic side elevational view of a simple signature consisting of four sheets;

a simple signature in the apparatus of FIG. 1;

FIG. If is a perspective view of a partly open simple signature and of certain elements in the apparatus of FIG. 1;

FIG. 2 is a schematic side elevational view of a more complex second signature wherein an additional sheet is attached to one outermost sheet of a simple signature;

FIG. 2a is a fragmentary schematic partly elevational and partly vertical sectional view of the apparatus during a first stage of opening of a signature of the type shown in FIG. 2;

FIGS. 2b and 2c illustrate further stages in opening of the signature shown in FIG. 2a;

FIG. 2d is a fragmentary partly elevational and partly sectional view of a larger part of the apparatus, an opened signature of the type shown in FIG. 2 being shown during transfer onto a support;

FIG. 3 is a schematic side elevational view of a more complex'third signature wherein one outermost sheet of the basic section is connected with two additional sheets;

FIG. 3a is a fragmentary schematic partly elevational and partly sectional view of the apparatus during a first stage of opening of a signature of the type illustrated in FIG. 3;

FIG. 3b illustrates the structure of FIG. 3a and shows the signature in the process of lifting the second additional sheet;

FIG. 30 illustrates the structure of FIG. 3b and shows the signature in the process of lifting the upper half of its basic section;

FIG. 3d is a fragmentary partly elevational and partly vertical sectional view of a larger part of the apparatus shown in FIGS. 3a-3c, further showing an opened signature during transfer onto a support;

FIG. 4 is a transverse vertical sectional view as seen in the direction of arrows from the line IV-IV of FIG. lb; and

FIG. illustrates the control system for the apparatus of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIGS. 1 and 4, there is shown an apparatus for opening of simple signatures (hereinafter called sections) 15 one of which is illustrated in FIG. la. This section comprises four sheets A, B, C, D having a common transverse edge or rib E and two longitudinal edges or ribs F, G which respectively connect the sheets A-B and C-D. The sheets B, C are the two inner or center sheets of the section 15 and should be moved apart prior to introduction of the section into a book binding or like machine, not shown.

The apparatus of FIGS. 1 and 4 comprises a housing or frame 100 which supports a conveyor including endless flexible elements or chains 1, 2 and a plurality of transversely extending entraining or transporting members in the form of rungs 3. The rungs 3 are preferably adjustable so that they can be moved closer to or further away from each other. As shown in FIG. I, the distance between successive pairs of rungs 3 is such that they can support a signature 15 which is fed thereto in any conventional way, not shown in the drawing. It suffices to say that when a pair of rungs 3 reaches the positions shown in the rightmost portion of FIG. 1, they support a section 15 in such a way that the common edge E extends transversely of the direction of travel of chains 1, 2 and that it rests on the rear rung 3. The front rung 3 supports the front marginal portion of the lowermost sheet D. A gripper 5 of the conveyor automatically clamps and holds the trailing edge E against movement with reference to the adjacent rung 3 while the section 15 travels with the chains 1, 2 along a horizontal first portion of an elongated endless path 7 toward an ejecting or transfer station which accommodates a stationary wedge-shaped support 10. The chains 1, 2 are trained over sprocket wheels 8 of which only one is shown in FIG. 1. The path 7 includes an arcuate second portion which is located at a level between the horizontal portion and the support 10.

The grippers 6 shown in FIG. 1 are caused to automatically engage the front edges of center sheets C in successive sections 15 upon opening of such sections. Reference should be had to the section 15A which is shown in FIG. 1 adjacent to the support and which is about to be accepted by this support. The surfaces 10a, 10b of the support 10 thereupon hold the center sheets B, C of the opened section A against movement toward each other.

As stated above, the first portion of the path 7 is preferably horizontal or substantially horizontal so that the sheets of flat- ,tened sections 15 which are deposited onto the corresponding rungs 3 are located in substantially horizontal planes A retaining shroud 9 which is suitably curved is outwardly adjacent to the end turn which includes the illustrated sprocket wheel 8 and serves to prevent closing of sections 15 which approach the support 10. The inner side of the shroud 9 engages the inner side of the center sheet 8 and holds this sheet against pivotal movement toward the fully exposed sheet C which latter is held by the associated gripper 6. When an opened section 15A is accepted by the support 10, i.e., when the corresponding grippers 5, 6 release the section, the respective pair of rungs 3 travels along the lower stretch of the path 7 and back toward the station where it receives a fresh section 15.

The raising station or raising means of the apparatus shown in FIG. 1 comprises a line of raising devices each including a pair of suction heads 11, l2, 13 which are adjacent to and located above the horizontal portion of the endless path 7. The pairs of suction heads 11, 12, 13 are respectively supported by and are freely oscillatable on transversely extending carriers ll, 12', 13' which serve to connect them with a pump 21 or another suitable suction generating device shown in FIG. 5. It is clear that the apparatus may comprise more than three pairs of suction heads and/or that each such pair can be replaced by a single suction head or three or more suction heads.

The apparatus further comprises control means for automatically sealing the suction heads 11 and 12 from the pump 21 in response to detection of partially opened sections 15. Such control means includes photosensitive detectors each comprising a light source 11', 12" and an aligned photosensitive receiver 14. When the light beam 15' (FIG. If) between the light source 11 or 12" and the associated receiver 14 is interrupted by a passing section 15, the receiver 14 causes a valve 23 or 24 (FIG. 5) to automatically seal the suction heads 11 or 12 from the pump 21 and to thus permit return movement of the corresponding sheet or sheets to the initial (folded) position. The last suction heads 13 are not controlled by a photosensitive detector; this is due to the fact that only these suction heads are needed for proper opening of sections 15 because the sheets A, B of successive sections 15 can be lifted as a unit during travel along the last station or suction heads 13, Le, just before they reach the retaining shroud 9.

The manner in which the receiver 14 which is associated with the light source 11 disconnects the suction heads 11 from the pump 21 is shown in FIG. 1 f. When the suction heads 11 engage the topmost sheet A of a passing section 15, such sheet is moved away from the sheet B whereby the partially displaced sheets A, B interrupt the light beam 15 between the receiver 14 and light source 11" so that the associated valve 23 closes and seals the suction heads 11 from the pump 21. Therefore, the sheet A can return into abutment with the sheet B. The same procedure is repeated when the section 15 thereupon advances along the suction heads 12 (which again lift the sheet A) and thereupon between the light source 12" and the associated receiver 14. The grippers 5, 6 can be opened and closed by suitable trips or cams which are mounted adjacent to the path 7 to automatically engage or release the sections during travel from the feeding station toward the support 10.

The operation:

FIG. lb shows a section 15 whose rear edge E rests on a trailing rung 3 and whose leading edges rest on the adjacent rung 3. The gripper 5 is operative and clamps the edge E to the adjacent rung but the gripper 6 is open so that the upper sheets A, B can be readily lifted and pivoted away from the sheet C. The section 15 is shown in a position in which the leading edge of its topmost sheet A is engaged by the suction heads 11 which are connected to the suction pump 21 so that the front part of the sheet A is partially lifted above and away from the sheet B. The suction heads 11 are free to oscillate about the axis of the carrier 11 (compare FIGS. lb and 10). When the chains 1, 2 advance the section 15 to the position shown in FIG. 10, the sheets A and B interrupt the light beam between the light source 11" and the aligned receiver 14 so that the suction heads 11 are disconnected from the suction pump 21 and release the sheet A which returns into abutment with the sheet B. The same procedure is repeated when the sheet A advances along the suction heads 12 which move it away from the sheet B and are thereupon disconnected from the suction pump 21 by the associated receiver 14 (light source 12".) so that the sheet A again returns into abutment with the sheet B. This is shown in FIGS. 1c and 1d.

However, when the topmost sheet A reaches the suction heads 13, these suction heads engage and hold the sheet A while the section 15 continues to move toward the retaining shroud 9 (FIG. 1e). Also, the front gripper 6 automatically engages the leading edge of the sheet C as soon as the sheets A and B (which are joined to each other by the edge F) are sufficiently lifted above and away from the sheet C. The sheets A, B are pivoted as a unit and the inner side of the sheet B thereupon engages the inner side of the retaining shroud 9 which holds the sheets A, B against return movement toward the sheet C (this is indicated in FIG. 1e by broken lines) while the section 15 travels along the arcuate portion of the path 7. The grippers 5, 6 automatically release the opened section 15A in an optimum position for transfer onto the support whereby the section is ready to be fed into thebookbinding machine.

It will be seen that the suction heads 11, 12 of FIGS. 1 to 1e need not perform any useful function, excepting, perhaps to ensure that the suction heads 13 can readily lift the sheets A, B above and away from the sheet C. These suction heads are shown merely for the purpose to illustrate that a minimal number of additional parts are necessary to use the same machine for opening of simple signatures (sections) or for opening of signatures which comprise a basic section and one or more additional sheets. The section which moves in the channel between the front sprocket wheels 8 and the shroud 9 is automatically separated from the suction heads 13 because the clamping action of grippers 5, 6 is stronger than the suction in these heads.

The signature 115 of FIG. 2 comprises a basic section 16 which is identical with the section of FIG. 1 and an additional sheet or panel 17 which is attached to and is outwardly I adjacent to the sheet A. In order to properly open the signature 115, the sheets 17, A and B must be pivoted above and away from the lower center sheet C.

When a signature 115 is placed onto the rungs 3 in a manner as shown in FIG. 2a, the rear gripper 5 engages the common edge E but the front gripper 6 is open. The suction heads 11 then engage the additional sheet 17 and pivot it above and away from the sheet A of the section 16. The first detector including the light source 11" and the associated receiver 14 is inactive because the additional sheet 17 is connected to the section 16 only along the trailing edge E. Therefore, the suction heads 11 continue to hold the sheet 17 while the sheet A advances into the range of the suction heads 12 (FIG. 2b) which lift it above the sheet B so that the detector including the light source 12" and the associated receiver 14 responds and seals the suction heads 12 from the pump 21. Thus, the sheet A is free to return into abutment with the sheet B. The sheet A is thereupon engaged by the suction heads 13 (FIG. 20) which hold it in the same way as shown in FIGS. ld-le while the sheet 17 moves past the suction heads 11 and travels below the carrier 12' (FIG. 2d) so that it cannot interfere with proper engagement between the suction heads 13 and the sheet A. The manner in which the thus opened signature 115A is thereupon caused to move along the retaining shroud 9 and is transferred onto the support 10 is illustrated in FIG. 2d.

It will be seen that the apparatus of FIG. 1 is capable of manipulating simple signatures (sections 15) as well as more complex signatures (115) by the simple expedient of employing a battery or series of suction heads some of which are controlled by photosensitive detectors or like control means to ensure that each sheet above the lower center sheet (C) is pivoted above and away from the sheet C prior to removal of signatures from the path 7.

FIG. 3 illustrates a still more complex signature 215 which comprises a basic section 18 and two additional sheets or tables 19, 20 which are outwardly adjacent to the sheet A and are connected to the section 18 along the trailing edge E". In order to open this signature 215, the sheets 19, 20 and A-B must be pivoted above and away from the lower center sheet C of the basic section 18. The manner in which such opening takes place is shown in FIGS. to .3d.

When the signature 215 is deposited onto a pair of rungs 3 (FIG. 3a) and the edge E" is engaged by the gripper 5, the suction heads 11 grip the front edge of the outer additional sheet 19 and pivot it above and away from the sheet 20. The first control unit remains ineffective because the sheet 19 is connected to the sheet 20 and section 18 only along the trailing edge E". The suction heads 11 then pivot on the carrier 1 I as indicated by the arrow and keep the sheet 19 away from the sheet 20 so that the latter can be engaged by the suction heads 12 (FIG. 3b) which thereupon pivot the sheet 20 and expose the sheet A which is engaged and lifted by the suction heads 13 (FIG. 30). The suction heads 13 also lift the sheet B which is joined to the sheet A along the edge F. The manner in which the thus opened signature 215A is thereupon deposited on the support 10 is shown in FIG. 3d. Thus, the apparatus of FIG. 1 can manipulate three types of signatures (15, 115, 215) and requires no adjustment whatever. It is further clear that the apparatus can manipulate signatures wherein one or more additional sheets are attached to the sheet C and/or D. Such additional sheets simply remain in their original positions while the suction heads 11, 12, and/or 13 pivot the sheets A-B and one or more additional sheets (17 or 19-20). If one or more additional tables or sheets must be provided between the two center or inner sheets B, C of a basic signature or section, they are preferably affixed to the sheet C so that they need not be lifted during transport toward the support 10.

The elements of the control means for the suction heads 11 and 12 are of commercially available type. They are preferably designed to react with a minimum of delay so as to permit opening of large numbers of signatures per unit of time. FIG. 5 merely shows a suction line 22 which connects the pump 21 directly with the carrier 13'. The carriers 11' and 12 are connectable with the line 22 by way of the valves 23, 24 which are respectively controlled by solenoids 23 and 24'. The connections between the solenoids 23, 24' and the detectors 11"14, l2"l4 include amplifiers 25, 26 which are connected to power leads 27. The solenoids 23',24 are energized and close the valves 23,24 when passing signatures respectively interrupt the light beams 15 between the light sources 11', 12" and the associated receivers 14.

It is clear that the improved apparatus is susceptible of many additional modifications without departing from the spirit of the present invention. For example, when the apparatus is used for opening of simple signatures or sections (15), the suction heads 11 and 12 can be removed or temporarily inactivated. The same holds true for the suction heads 11 or 12 if the apparatus is used for opening of signatures (FIGS. 2-2d). Furthermore, the apparatus can be used for opening of so-called parallel folds" signatures with or without glued sheets.

It is further clear that the operation of the apparatus can be programmed so that the various suction heads are connected to and/or disconnected from a suction generating device in accordance with a predetermined schedule. The programming means may include electronic, electromagnetic, pneumatic, and/or mechanical elements and its operation will be selected as a function of the desired composition of the book. Such programming means then replaces the illustrated control means and regulates the drive for the chains 1, 2 as well as the timing of intervals during which the suction heads are connected to and disconnected from the suction generating means.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features which fairly constitute essential characteristics of the generic and specific aspects of my contribution to the art and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. A method of opening a plurality of sheets connected at one edge thereof to each other, said sheets being superimposed on each other and comprise at least one signature having a pair of center sheets and a pair of outer sheets respectively connected to each other at edges thereof extending in a direction transverse to the direction of said one edge, said method comprising the steps of conveying said sheets along a path past a plurality of raising stations, including a last station, spaced from each other, said path extending at each point substantially in the direction of the transverse edges; raising the uppermost sheet and pivoting it about said one edge; detecting whether the sheet being raised is an outer signature sheet;

releasing the raised sheet if it is an outer signature sheet or maintaining the raised sheet in raised position while said sheets advance along said path beneath the stations preceeding said last station if said sheet is not an outer signature sheet; raising an outer signature sheet together with a center signature sheet connected thereto at said last station to open and maintain said signature in open condition; and depositing the sheets in open condition on a stationary member spaced from said path.

2. A method as defined in claim 1, wherein said one edge of said sheets is the trailing edge of said sheets during travel along said path and wherein the sheets advance in a substantially horizontal plane during travel toward said position spaced from said path where said sheets are deposited.

3. A method as defined in claim 2, wherein said raising and pivoting step comprises engaging and holding the sheets by suction.

4. Apparatus for opening a plurality of sheets connected at one edge thereof to each other, said sheets being superimposed on each other and comprise at least one signature having a pair of center sheets and a pair of outer sheets respectively connected to each other at an edge thereof extending in a direction substantially transversely to the direction of said one edge, said apparatus comprising conveyor means for conveying said sheets along a path extending in a direction transverse to said one edge; a plurality of raising stations spaced from each other along said path and including a last station, each of said raising stations comprising raising means operative to raise the uppermost sheet of the sheets as they pass the respective station and pivoting said sheet about said one edge; at least one control means located adjacent to said path and intermediate two raising stations for detecting whether the sheet raised between said two raising stations is an outer signature sheet, said detecting means cooperating with said raising means for releasing the raised sheet if it is an outer signature sheet or maintaining the raised sheet in raised position while said sheets advance along said path if said sheet is not an outer signature sheet; and support means spaced from said path following said last raising station adapted to receive said sheets in open condition.

5. Apparatus as defined in claim 4, wherein said conveyor means includes an endless conveyor and said path includes a substantially horizontal first portion along which the signatures are transported past said raising means and an arcuate second portion located between said horizontal portion and said support means, said support means being located at a level below said first portion.

6, Apparatus as defined in claim 5, wherein said conveyor comprises entraining means for said sheets and gripper means for separably coupling the common edges of said sheets to the respective entraining means during travel along said first and second portions of said path.

7. Apparatus as defined in claim 6, wherein said conveyor further comprises second gripper means for separably coupling the other center sheets of said signatures to the respective entraining means upon opening of said signatures and prior to transfer of such signatures to said support means.

8. Apparatus as defined in claim 4, wherein said raising means comprises at least one device for raising the sheets of successive sheets by suction.

9. Apparatus as defined in claim 8, wherein said device is oscillatable about a substantially horizontal axis extending transversely of the direction of travel of said sheets past said raising means.

10. Apparatus as defined in claim 4, wherein each of said raising means comprises at least one suction head and said control means comprises photosensitive detector means.

11. Apparatus as defined in claim 10, wherein said photosensitive detector means is arranged to deactivate all but a single one of said control means in response to detection of successive signatures, said control means forming a series along said conveyor means and said single control means being the last of said series as considered in the direction of travel of said sheets.

12. Apparatus as defined in claim 4, wherein said path includes a first portion adjacent to said raising means and an arcuate second portion between said first portion and said support means, and further comprising retaining means for holding said sheets in open positions during travel along said second portion of said path.

13. Apparatus as defined in claim 12, wherein said retaining means comprises an arcuate shroud and wherein said support means is closely adjacent to and located below said second portion of said path.

14. Apparatus as defined in claim 4, wherein said conveyor means comprises at least one endless flexible element and includes an end turn disposed at a level between said raising means and said support means. 

1. A method of opening a plurality of sheets connected at one edge thereof to each other, said sheets being superimposed on each other and comprise at least one signature having a pair of center sheets and a pair of outer sheets respectively connected to each other at edges thereof extending in a direction transverse to the direction of said one edge, said method comprising the steps of conveying said sheets along a path past a plurality of raising stations, including a last station, spaced from each other, said path extending at each point substantially in the direction of the transverse edges; raising the uppermost sheet and pivoting it about said one edge; detecting whether the sheet being raised is an outer signature sheet; releasing the raised sheet if it is an outer signature sheet or maintaining the raised sheet in raised position while said sheets advance along said path beneath the stations preceeding said last station if said sheet is not an outer signature sheet; raising an outer signature sheet together with a center signature sheet connected thereto at said last station to open and maintain said signature in open condition; and depositing the sheets in open condition on a stationary member spaced from said path.
 2. A method as defined in claim 1, wherein said one edge of said sheets is the trailing edge of said sheets during travel along said path and wherein the sheets advance in a substantially horizontal plane during travel toward said position spaced from said path where said sheets are deposited.
 3. A method as defined in claim 2, wherein said raising and pivoting step comprises engaging and holding the sheets by suction.
 4. Apparatus for opening a plurality of sheets connected at one edge thereof to each other, said sheets being superimposed on each other and comprise at least one signature having a pair of center sheets and a pair of outer sheets respectively connected to each other at an edge thereof extending in a direction substantially transversely to the direction of said one edge, said apparatus comprising conveyor means for conveying said sheets along a path extending in a direction transverse to said one edge; a plurality of raising stations spaced from each other along said path and including a last station, each of said raIsing stations comprising raising means operative to raise the uppermost sheet of the sheets as they pass the respective station and pivoting said sheet about said one edge; at least one control means located adjacent to said path and intermediate two raising stations for detecting whether the sheet raised between said two raising stations is an outer signature sheet, said detecting means cooperating with said raising means for releasing the raised sheet if it is an outer signature sheet or maintaining the raised sheet in raised position while said sheets advance along said path if said sheet is not an outer signature sheet; and support means spaced from said path following said last raising station adapted to receive said sheets in open condition.
 5. Apparatus as defined in claim 4, wherein said conveyor means includes an endless conveyor and said path includes a substantially horizontal first portion along which the signatures are transported past said raising means and an arcuate second portion located between said horizontal portion and said support means, said support means being located at a level below said first portion.
 6. Apparatus as defined in claim 5, wherein said conveyor comprises entraining means for said sheets and gripper means for separably coupling the common edges of said sheets to the respective entraining means during travel along said first and second portions of said path.
 7. Apparatus as defined in claim 6, wherein said conveyor further comprises second gripper means for separably coupling the other center sheets of said signatures to the respective entraining means upon opening of said signatures and prior to transfer of such signatures to said support means.
 8. Apparatus as defined in claim 4, wherein said raising means comprises at least one device for raising the sheets of successive sheets by suction.
 9. Apparatus as defined in claim 8, wherein said device is oscillatable about a substantially horizontal axis extending transversely of the direction of travel of said sheets past said raising means.
 10. Apparatus as defined in claim 4, wherein each of said raising means comprises at least one suction head and said control means comprises photosensitive detector means.
 11. Apparatus as defined in claim 10, wherein said photosensitive detector means is arranged to deactivate all but a single one of said control means in response to detection of successive signatures, said control means forming a series along said conveyor means and said single control means being the last of said series as considered in the direction of travel of said sheets.
 12. Apparatus as defined in claim 4, wherein said path includes a first portion adjacent to said raising means and an arcuate second portion between said first portion and said support means, and further comprising retaining means for holding said sheets in open positions during travel along said second portion of said path.
 13. Apparatus as defined in claim 12, wherein said retaining means comprises an arcuate shroud and wherein said support means is closely adjacent to and located below said second portion of said path.
 14. Apparatus as defined in claim 4, wherein said conveyor means comprises at least one endless flexible element and includes an end turn disposed at a level between said raising means and said support means. 